Furnace



May 24, 1938. P. c. TEMPLE 2,118,121

' FURNACE Filed April 16, 1935 2 Sheets-Sheet l PAUL. C; TEMPLE May 24, 1938. p c, TEMPLE 2,118,121

FURNACE Filed April 16, 1955 2 Sheets-Sheet 2 242824 Z824 If 4 5km: C. 'TEMPLE Patented May 24, 1938 UNITED STATES ATENT OFFICE FURNACE Delaware Application April 16, 1935, Serial No. 16,670

10 Claims.

This invention relates to furnaces, and more particularly to furnaces having means for controlling the flow and distribution of air for combustion of fuel.

In the operation of multiple retort underfeed stokers, the fuel is delivered to the front ends of spaced parallel retorts separated by rows of tuyere blocks. The tuyere blocks are supplied with air under pressure, and the fuel is burned as it moves slowly toward the rear of the furnace, Where the ash is discharged. Since combustion proceeds slowly and progressively, the portion of the fuel bed at the front of the furnace has widely different characteristics from the portion at the rear of the furnace. Consequently, the air requirements for the best combustion conditions likewise differ from front to rear of the furnace. Moreover, the rate of air flow to any small portion of the fuel bed is largely a function of the resistance of the fuel, which in turn depends upon its degree of fineness, its compactness, and its thickness. The air tends to flow more rapidly through thin spots in the fuel bed, increasing the rate of combustion over small localized areas, and thus aggravating the condition. As a result groups of tuyere blocks may become exposed to the heat of the furnace and thusbe destroyed.

It is accordingly the main object of the present invention to overcome these difficulties and to provide a furnace having means for distributing air for combustion accurately and in a desired manner.

It is a further object of the invention to provide a furnace having means to maintain a desired rate of air flow to different portions of the fuel bed irrespective of variations in the resistance of the fuel bed.

It is a further object of the invention to provide a furnace having means. to maintain a desired rate of air flow to different portions of the fuel bed, and means for adjusting the rate of air flow to certain portions of the fuel bed as compared with other portions.

It is a further object of the invention to provide a furnace having means to distribute air for combustion in a desired manner to different portions of the fuel bed, and means for varying the total air flow without altering the relative distribution.

It is a further object of the invention to provide a furnace of the underfeed type having means to control the distribution and rate of flow of the air to the tuyre blocks.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a longitudinal section through a portion of an underfeed stoker furnace having means for controlling the flow and distribution of the air for combustion;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a rear elevation of a control panel; and

Fig. 4 is a section on the line 4--4 of Fig. 3.

In the drawings I have shown an underfeed stoker I having retorts II which extend rearwardly from the front wall l2 of a furnace H. The retorts are separated by the usual rows of tuyere blocks l5 which form the stoker grate surface and distribute air to the fuel bed. Vertical ducts I6 are located beneath the retorts H, and the upper portion of each duct is divided into two branches, as shown in Fig. 2, these branches leading to tuyere blocks on opposite sides of the retorts. The ducts it are arranged in rows both longitudinally and transversely of the stoker, and each duct delivers air to a comparatively small portion of the stoker grate surface.

Each duct I6 is supplied with air at a predetermined rate which remains unaffectedby variations in the resistance of the fuel bed. For this pur-.- pose I utilize a number of positive displacement blowers !8, each duct I6 having a blower 3 connected to its lower end. By the term positive displacement blower I mean a blower of any suitable construction which will maintain a rate of air flow in substantially direct proportion to the blower speed irrespective of the resistance to flow. The blowers illustrated are of a wellknown type having two rotors I 9 which revolve in opposite directions. A siftings trap 20 is preferably provided in each duct Hi to prevent fine coal from dropping into the blower therebeneath.

The blowers l8 are preferably arranged in groups, and means is provided for varying the speed of each group relative to that of the others. In a stoker furnace the fuel bed varies greatly from front to rear, and the air requirements for the best combustion conditions likewise vary. It i therefore desirable to provide means whereby the air flow in the ducts I 6 in each transverse row can be controlled independently of the air flow in the ducts of the other rows. For this purpose the blowers l8 associated with each transverse row of ducts are arranged with their shafts 2| in axial alignment and suitably coupled together for actuation by a directly connected electric motor 22 of the variable speed type.

For convenience in controlling the speed of the motors 22, I preferably utilize a vertical control panel 23. 0n the rear of the panel are mounted a plurality of rheostats 24, one for each of the motors 22. It will be understood that these rheostats are electrically connected in a well-known manner to their respective motors and to a power line 25, asshown in Fig. 2, so that the motor speeds may be regulated. Each rheostat is provided with a pinion 2B which engages a gear segment 2? on one end of a pivotally supported lever 28. The levers 23 are connected by rods 39'to arms 3| mounted on a rotatably adjustable horizontal shaft 32. The effective lengths of the arms 3! are manually adjustable to permit a control over the relative settings of the rheostats. For this purpose each arm is provided with a nut 34 which is connected to the corresponding rod 38. Each nut 34 is mounted on a screw 35 which can be rotated by means of a handwheel 36 located at the front of the panel and acting through suitable gearing 38. As the handwheel is turned to rotate the screw, it actuates a suitable indicator 39 on the front of the panel by means of a flexible shaft located within a tube 40. ,The construc tion of the arms 3| and associated parts is more fully disclosed in my prior Patent No. 1,977,024 dated October 16, 1934.

The horizontal shaft 32 is preferably adjusted automatically in accordance with the demand for heat. For this purpose I have shown an automat ic regulator 42 connected by means of a rod @3 to an arm 4d mounted on the shaft 32. If the stoker I!) is used for steam generation, as is usually the case, the regulator 42 will be arranged to respond to variations in the pressure of the steam in a well-known manner.

As an aid to the operator in maintaining the proper combustion conditions, I preferably'provide tachometers 46 (Fig. 1) on the panel 23 to indicate the speed of rotation of the motors 22. Since the air flow to each transverse zone of the stoker is directly proportional to the speed of the corresponding motor, these instruments can be calibrated to indicate cubic feet of air per minute if desired.

In some cases it may be desirable to supply air to the blowers H3 at a pressure above atmospheric. For this purpose I have shown the blowers mounted within a chamber 4'! formed by walls 48. A fan 50 is arranged to supply air to the chamber 47 and dampers 5| are provided to control the rate of air flow.

The operation of the invention will now be apparent from the above disclosure. The fan 50 de livers air to the chamber 41, and the blowers l8 deliver air from the chamber 47 through the ducts 16 to the tuyere blocks Hi. The rate of air flow in each duct depends solely upon the speed of the corresponding blower and is independent of the fuel bed resistance. Hence, if one portion of the fuel bed becomes slightly thinner than another portion similarly located with respect to the front wall l2, the thin portion will receive no more air than the thick portion, and there is no danger of exposing and burning the tuyere blocks. By adjusting the handwheels 36 it is possible to vary the effective lengths of the arms 3! and thus vary the relative settings of the rheostats 24. These in turn control the relative speeds of the motors 22, which are indicated by the tachometers 46. In this manner the operator can conveniently control the relative distribution of the air from front to rear of the stoker. As the demand for heat varies, the automatic regulator 42 will turn the shaft 32 and readjust all the rheostats 24. This will vary the total air flow to the furnace without affecting its relative distribution. If the fan 5!! is'omitted, the blowers [8 will receive air at atmospheric pressure, and the load imposed upon the motors 22 will be increased. Any fine fuel which sifts through the tuyre blocks l5 will be caught in the traps 2!! and thus prevented from damaging the blowers l8, which are constructed with rather close clearances. These traps can be emptied from time to time as may be required.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: r I

1. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, and

means to vary the speed of operation of one group of blowers relative to another.

2. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, and a separate variable-speed motor to drive each group of blowers.

3. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, a separate variable-speed electric motor to drive each group of blowers, and a separaterheostat to control the speed of each motor.

4.'A furnace comprisinga grate surface divided both longitudinally and transversely into I comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, a separate variable-speed motor to drive each group of blowers, a separate adjustable speed control device for each motor, means to adjust each speed control device relative to the others, and means to adjust all the speed control devices simultaneously without varying their relative adjustments.

5. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating.

with one of said areas, a positive displacement blower connected to each duct to supply air there- 7 to, the blowers being arranged in groups correspondng to the transverse rows of ducts, a separate variable-speed electric motor to drive each group of blowers, a separate rheostat to control the speed of each'motor, means to adjust each rheostat relative to the others, and means to adjust all the rheostats simultaneously without varying their relative adjustments,

6. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of trans verse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, a separate variable-speed electric motor to drive each group of blowers, a separate rheostat to control the speed of each motor, a device adjustable to difierent positions, and independently adjustable connections between the device and each rheostat, whereby all the rheostats can be adjusted simultaneously by means of said device, to control the total air supply, and each rheostat can be adjusted independently of the others by means of the corresponding adjustable connection, to control the relative distribution of the air supply.

7. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, a separate variable-speed electric motor to drive each group of blowers, a separate rheostat to control the speed of each motor, a rotatably adjustable shaft, a plurality of arms mounted on the shaft, connections between the arms and the rheostats, and means to vary the effective length of each arm.

8. A furnace comprising a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air there to, the blowers being arranged in groups corresponding to the transverse rows of ducts, a separate variable-speed electric motor to drive each group of blowers, a separate rheostat to control the speed of each motor, a rotatably adjustable shaft, an automatic regulator connected to the shaft to actuate the same, a plurality of arms mounted on the shaft, connections between the arms and the rheostats, and means to vary the effective length of each arm.

9- A furnace of the progressive-feed type comprising a front wall, means providing a grate surface extending rearwardly from said wall and divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups: corresponding to the transverse rows of ducts, and means to vary the speed of operation of one group of blowers relative to another.

10. A furnace of the multiple-retort underfeed type comprising a front wall, a plurality of retorts extending rearwardly from said wall, rows of tuyre blocks located between the retorts and providing a grate surface divided both longitudinally and transversely into comparatively small areas, a plurality of transverse rows of ducts, each duct communicating with one of said areas, a positive displacement blower connected to each duct to supply air thereto, the blowers being arranged in groups corresponding to the transverse rows of ducts, and means to vary the speed of operation of one group of blowers relative to another.

PAUL C. TEMPLE. 

